Disabling ListAgents throws NoSuchToolError during HarnessAgent construction

Constructing HarnessAgent with inactiveTools: ['ListAgents'] throws AI_NoSuchToolError before a session starts. The message is Model tried to call unavailable tool 'ListAgents'.

Difficulty

Easy

Time

~5 min

Steps

Fixed in

ai@7.0.143

Last checked

Oct 19, 2026

Verified fix: PR #22383 merged on 2026-10-09. Fixed in ai@7.0.143 (first published release whose tag contains the merge commit). Last checked 2026-10-19.

Symptom

Constructing HarnessAgent with inactiveTools: ['ListAgents'] throws AI_NoSuchToolError before a session starts. The message is Model tried to call unavailable tool 'ListAgents'.

Evidence what you'll see

Despite that wording, no model attempted a tool call. The exception is thrown synchronously in the constructor.
The same configuration using the registered SendMessage succeeds. TypeScript also rejects ListAgents as an unknown tool name.
ListAgents is a native tool in the pinned coding-agent runtime, but the adapter's builtin catalog did not declare it.

Why it happens

The harness adapter omitted ListAgents from its built-in catalog, so HarnessAgent built the available-tool set without that name and the filter validator rejected it. Pull request 22383 registers ListAgents with its native input and output schema and keeps deny-list forwarding.

Affected versions

The coding-agent harness adapter at commit e00b1b14e99b. The linked issue does not name an ai package version beyond that commit, or an operating system.

Fix steps

0 of 2 done

Step 1Upgrade to ai@7.0.143 or a later tag that contains pull request 22383.
Step 2The linked issue does not give a constructor workaround that disables ListAgents on the catalog that omitted it.

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How to check it worked

new HarnessAgent({ inactiveTools: ['ListAgents'] }) constructs without AI_NoSuchToolError.

If it still fails

Unknown tool names in inactiveTools are still rejected. The linked issue does not describe AI_NoSuchToolError for ListAgents on ai@7.0.143.

Sources and credit

Summarized in our own words from these public reports. Credit goes to their authors.

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